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Published byErika Opal Mitchell Modified over 9 years ago
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Kayla Hartwell 1, Hugh Notman 1,2, & Mary Pavelka 1 1 University of Calgary and 2 Athabasca University, Alberta, Canada
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Described in a number of studies (Campbell 2003; Link et al. 2009; Slater et al. 2009) Low intensity intra-group aggression directed from males to females “Stereotyped displays and chases” (Link et al. 2009) Photo: Kayley Evans
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Sexual Segregation and Aggregation Statistic (SSAS) (Bonenfant et al. 2007) Association = presence in the same subgroup using 30min subgroup scan data Distinguishes active segregation and aggregation from random association Calculates index value ranging from 0 (significant aggregation) to 1 (significant segregation)
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1 Jan Mar May Jul Sep Nov 0.5 0 SSAS Month (Segregation) (Aggregation)
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1.Compare rates of aggression by Males to females Males to males Females to males Females to females 2.Compare the contexts in which these aggressive interactions occurred
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34 - 38 group members over course of study 2008-2011 All individuals habituated and individually recognizable Year MaleFemales AdultSubadultAdultSubadult 200832113 200932122 201052124 201153132
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Collect scan & focal data All observations of fission- fusion events & aggression For aggression: ID of director(s) & receiver(s) & context ~2000 contact hours over 601 days 193 aggressive interactions
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Food: receiver was feeding when aggression occurred Fusion: subgroup fusion occurred within 5min of aggression (food took precedence over fusion) Sexual: copulation, place sniff, genital inspect occurred immediately following aggression Other: any other context
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Results 80% M-F (N=154) 15% F-F (N=30) 3% F-M (N=5) 2% M-M (N=4)
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Context of aggression differed between M-F & F-F ( X 2 = 12 df=3 P =.007) M-F occurred most often during subgroup fusions (38%) or feeding (31%) F-F occurred most often during feeding (41%) or other (45%)
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Sociogram of asymmetric matrix of dyadic aggression rates (arrow points from director to receiver) Males Females Aggression rate/hour
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Patterns of female- directed aggression at Runaway Creek are consistent with that found at other Ateles sites Results support Link et al. 2009: M-F aggression is a form of social control (indirect sexual coercion) May encourage sexual segregation as females try to avoid attacks from males
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Brittany Dean, Kayley Evans, & Jane Champion Stevan Reneau, Gilroy Welch, & Birds Without Borders Dr. Tak Fung Natural Sciences and Engineering Research Council of Canada, University of Calgary, & National Geographic
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XY = total number of males and females sampled k = total number of subgroups sampled i = selected subgroup N i = subgroup size X i Y i = number of males and females is a subgroup
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